The present invention relates to novel bis-dioxopiperazine derivatives and non-toxic salts thereof, process for their preparation, antitumor agents comprising them and compositions containing them.
Bis-dioxopiperazine derivatives of the present invention are represented by the following general formula (I): ##STR2## wherein R represents an alkyl radical having 1 to 17 carbon atoms, a cycloalkyl radical having 3 to 7 carbon atoms, a lower alkyl radical having a substituent or substituents selected from the group consisting of halogeno, carboxy, alkoxycarbonyl having 2 to 5 carbon atoms, lower alkoxy, substituted or unsubstituted phenoxy, naphthyloxy, substituted or unsubstituted phenylthio, substituted or unsubstituted phenyl and naphthyl, a substituted or unsubstituted phenyl lower alkenyl radical, a substituted or unsubstituted phenyl radical, a naphthyl radical, a heterocyclic radical selected from the group consisting of pyridyl, furyl and thienyl, an alkoxy radical having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl lower alkoxy radical, or a substituted or unsubstituted phenoxy radical. A substituent or substituents on R may be selected from the group consisting of lower alkyl, halogeno, lower alkoxy, acyloxy having 2 to 5 carbon atoms, methylenedioxy, carboxy, amino, methanesulfonylamino and nitro. The above-mentioned "lower alkyl", "lower alkoxy" and "lower alkenyl" respectively refer to alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms and alkenyl having 2 to 4 carbon atoms.
Several kinds of bis-dioxopiperazine derivatives have been already reported. Especially 1,2-bis(4-morpholinomethyl-3,5-dioxopiperazin-1-yl)ethane is known as an analogue of the compound which the present invention concerns and its clinical efficacy as an antitumor and radio-potentiative agent was already evaluated (see Abstract, 8th International Congress of Pharmacology p441, 1981). However the known compound had a problem on the preparation because it is extremely unstable in the protic polar solvents such as water, lower alcohol and so on.
Based on the attractive biological activities of the known bis-dioxopiperazine derivatives, we, the inventors further carried out the synthesis studies on these derivatives with the excellent activity and pharmaceutically advantageous property. We found that the aforementioned bis-dioxopiperazine derivatives of general formula (I) exhibit broader spectra of antitumor activities, antimetastatic activity, pharmaceutically advantageous stability in the protic polar solvents, and lower toxicity, thus accomplishing the present invention.